Move construct_context.sh from Make to Soong. Update OWNERS list.

This script belongs with other manifest-related scripts, and the future
plan is to rewrite it in Python and share common functionality with
other scripts.

Test: lunch aosp_cf_x86_phone-userdebug && m
Bug: 132357300
Change-Id: I4b90129e5023ca1a2c818fc160c34b0b7da943ef